US President Donald Trump arrived in Rome on Friday for the funeral of Pope Francis, where he will brush shoulders with an array of world leaders on the unexpected first foreign trip of his second term.

Trump, who was accompanied by wife Melania, had a distant relationship with the late pontiff who criticized him sharply on his signature policy of mass deportations of migrants.

But Trump will be center-stage for a major diplomatic gathering on Saturday with some 50 heads of state, including 10 reigning monarchs, at the Vatican. 

Trump said it was possible he could meet Ukrainian President Volodymyr Zelensky in what would be the two leaders' first time together since a disastrous White House meeting on 28 February.

Trump and Vice President JD Vance in that meeting berated Zelensky, calling him ungrateful for the billions of dollars of US military assistance given since Russia invaded Ukraine in 2022.

Trump, while calling on Russia to stop its aerial attacks on Ukraine, has recently blamed Zelensky for the war and the continuing bloodshed.

Zelensky said he may miss the funeral however due to military meetings after a deadly Russian strike on Kyiv.

No meetings have been announced in Rome for Trump, who is due to stay only half a day.

Trump told reporters on Air Force One he would meet "some people" including Italian Prime Minister Giorgia Meloni, whom he hosted earlier this month at the White House to discuss tariffs.

But he said any meetings would be quick and added: "Frankly it’s a little disrespectful to have meetings when you’re at the funeral of the pope."

Trump may also find discomfort around some of the other mourners — chief among them his predecessor, Joe Biden.

Biden is a devout Catholic and was close with Francis. He will travel independently to Rome, his office said, even though former presidents generally travel on Air Force One for funerals. 

Trump has relentlessly attacked Biden and torn down his legacy in his nearly 100 days in office, with Biden in turn recently speaking out against Trump's policies.

President George W. Bush took two of his predecessors, Bill Clinton and his father, on Air Force One for Pope John Paul II's funeral in 2005.

EU talks?

Trump's trip to Italy comes after he rattled European allies by imposing sweeping tariffs, although he at least temporarily has backed down from the most severe measures.

French President Emmanuel Macron, one leader who has managed to forge a bond with Trump, and outgoing German Chancellor Olaf Scholz will be at the funeral, as will top EU officials Ursula von der Leyen and Antonio Costa.

Meloni had already extended an invitation to Trump to visit Rome before the pope's death, saying that it could provide an opportunity for talks with European leaders.

Also in attendance will be Brazilian President Luiz Inacio Lula da Silva, a veteran leftist whose vanquished rival Jair Bolsonaro is an ideological soulmate of Trump.

Lula has been critical of Trump but has avoided major confrontation since the Republican billionaire's return.

The funeral will also bring leaders more ideologically in tune with Trump including Hungarian Prime Minister Viktor Orban and President Javier Milei of Argentina, the late pope's home country.

Trump also paid a brief visit to France after his election but before his inauguration for the reopening of Notre Dame cathedral. Macron brought him together with Zelensky on the sidelines.

Trump's first foreign trip was supposed to be to the oil-rich Gulf Arab states, where he is hoping to see business opportunities and press them to accept closer relations with Israel.

He is to visit Saudi Arabia, Qatar and the United Arab Emirates from 13 May.

Trump will however be keeping one important appointment: with First Lady Melania Trump for her 55th birthday, which also falls on Saturday.

He told reporters he hadn't had time to buy any presents but added that "I'm taking her for dinner on Air Force One."